When an endless belt, e. g. a conveyor belt is continuously driven to move along a transport path that is defined by the rollers, manufacturing tolerances in the rollers and the bearing structures thereof as well as external influences may cause a tendency of the belt to move not only in longitudinal direction of the transport path but to move also in lateral direction, i.e. in axial direction of the rollers.
In order to suppress such lateral movements of the belt, it is known, e.g. from JP 2008-007246 A, to monitor the lateral position of the belt by means of a belt edge detector and to feedback-control the lateral movements of the belt by adjusting a tilt position of one of the rollers. When the roller is tilted about an axis that is normal to the axis of rotation of this roller, this has an effect on the direction of belt transport, so that the belt may be “steered” by appropriately controlling the tilt angle of the roller.
US 2010/0080598 A1 describes a belt adjusting mechanism wherein a lateral shift position of a transfer belt is changed in a belt shift direction perpendicular to the belt conveyance direction by changing an inclination angle of a shift control roller.
EP 2 073 066 A1 describes a similar mechanism. A correction roller is tilted by moving one end up and down.
U.S. Pat. No. 6,594,460 B1 describes a belt adjusting mechanism wherein the lateral position of the belt is adjusted by means of belt edge guides that engage the edges of the belt and are movable in axial direction of the rollers.
In certain applications, e.g. in high resolution print applications where image substrate sheets are supported on the endless belt and are conveyed past a processing stage, e.g. a print head, or the endless belt itself serves as an image carrier, it is important that the lateral position of the belt is controlled with very accuracy.